Sophisticated high density arrangements for the dry-housing of animals are known, in particular for mammalian laboratory animals such as mice, rats, rabbits, for breeding such animals, etc. A number of interests affect the design of animal housing systems. The welfare of the animals is a major concern, making it necessary to supply the animals with basic requirements of air, water and food. The animals must be sheltered if possible from diseases or parasites and also should be protected from unnecessary stress. It is advantageous to facilitate quick and convenient access to the enclosures containing the animals for providing services. In laboratory applications, those conducting lab tests need access to the animals to initiate testing, and means to observe or measure the effects. In other situations such as pet stores and hobbyists' installations, the animals also need to be accessible yet protected and in view.
Without compromising other interests, an optimal housing arrangement should be compact, namely the density of the animal population should be high. It should be neat and clean. It should be readily capable of occupying the same floor space as the humans that are providing services and/or conducting testing. The maintenance and use of the system should maximize comfort and minimize danger for both the animals and the humans, for example not only preventing potential catastrophe such as the transfer of a deadly disease, but also avoiding simple discomforts such as unpleasant odors or dispersion of allergens.
Some animals used in laboratory experiments, like rare pets, can represent a substantial investment. Rare pets are expensive to acquire, as are certain laboratory animals such as those having specific genetic characteristics or propensities that are useful for testing. Apart from the cost of the animals, the time and effort invested to carry on an experiment makes it important that most or all of the animals survive for the duration of the experiment. It is important that the animals stay healthy while housed and also that their management and upkeep be as convenient as practicable.
Examples of high density housing for mammals such as mice are disclosed, for example in U.S. Pat. Re. No. 32,113--Harr (Air conditioned laboratory rack for animal cages); U.S. Pat. No. 4,690,100--Thomas (Ventilated animal housing and service system with cage filter covers); U.S. Pat. No. 5,044,316--Thomas (Ventilated animal caging system with cage racks and filter covers including valves operable by rack); U.S. Pat. No. 5,474,024--Thomas (Caging system with slide bar operator for quick disconnect water fitting), and others. The disclosures of these patents are incorporated for their teachings regarding high density housing and protection from disease while supplying animals with the necessities of life.
Several of the foregoing patents use covers on animal cages to protect the occupants from airborne pathogens when the cages are removed from the rack. The "cages" are actually integrally hermetic transparent plastic boxes, closed on the bottom and sidewalls, and closed over the top by the cover. These cages are engaged against hollow shelves in the rack, subdivided internally to define air supply and exhaust conduits. The supply and exhaust conduits both have orifices placed to open into cages carried on one or both sides of the rack, such that the internal volume of the cage box becomes a part of an air flow path from the supply duct to the exhaust duct.
Various apparatus for supplying utilities such as food, water, and air to housings for laboratory animals are known in the art of laboratory animal housing of the type used for lab mice, etc. For example, U.S. Pat. No. 5,513,596 discloses a quick disconnect water supply assembly for removably coupling cages to a drinking water supply. A conduit is mounted to pass through the barrier defined by a wall of the cage box, and contains an occupant-operated valve. the water supply assembly couples into a water supply line when the cage is inserted into the rack. A linking member attaches to the water line for opening or closing the connection with the water line and a manually movable knob is operated to engage or disengage the cage with the water supply. The connection closes off the water supply when the cage is withdrawn from the cage rack system.
The drinking water supply as described is substantially a one way affair, namely with water flowing from the supply into the cage enclosure without a flow return. U.S. Pat. No. 5,174,239 discloses an aquarium device that is sealed and coupled to water fed under pressure into the aquarium body by a feed pump. The water pressure resulting from the pump causes used water in the aquarium body to be discharged through a drain pipe. The drain pipe is coupled to a filtration and aeration unit that leads into the feed pump, providing a closed circulation path including the aquarium volume and the filter/aerator in a closed loop. A closed loop filtration device for each aquarium is the normal filtration arrangement in a multiple-aquarium installation. Although many aquarium tanks may be disposed in relative proximity, each one has its own separate water pump and water filter, which arrangement avoids a sharing of water that might engender the spread of disease. Aeration supplies on the other hand are typically commonly coupled to flow lines leading into a number of tanks. No return is needed because the air discharge is by bubbling into the ambient air.
U.S. Pat. No. 5,042,425 discloses an aquarium and bird and animal containment system. The containment system includes racks for displaying one or more aquariums and racks for displaying bird and animal cages. A cabinet disposed between the aquarium support and the bird and animal support contains a sink, a water supply bringing water to the tanks and cages, and an air supply and distribution system bringing air to biological filters located in the aquarium tanks. An drain system carries away overflow water.
U.S. Pat. No. 5,197,409 discloses an aquatic tank display system suitable for use in a pet store or aquarium. The system includes a tank support frame having multiple tiers or levels for supporting tanks at different elevations. Portions of the frame are made of a non-corrosive material, because it is possible that areas around the tanks may get wet, and are non-conductive for avoiding electrical hazard. Each tank has an open top which is covered by a lamp fixture and a hinged lid.
U.S. Pat. No. 5,413,070 discloses a multiple tank display for a pet store or the like, comprising supports defining vertically spaced tiers. The tanks have transparent walls and those in the top and bottom tiers have front walls that are inclined to refract light and enhance viewing by a person standing in front of the display.
U.S. Pat. No. 5,365,886 discloses an aquarium containment system. Racks support multiple stacked sets of tanks and each rack has a removable lighting system. An automatic water distribution system is provided for the aquariums, including mechanical and biological filters and heaters. Sliding access panels facilitate access to the tops of the tanks for maintenance and cleaning purposes.
A problem encountered when using circulating water to supply aerated and/or filtered water to multiple tanks is that the water for all the tanks can be contaminated by pathogens originating in one of the tanks. As a result, a circulating water system may be disadvantageous. On the other hand, having a single filtration and distribution system serving a number of tanks has obvious conveniences and cost savings. A disease problem of a similar type is encountered with mammal cage systems in that airborne dander from one cage can spread pathogens to other cages. Uncovered cages can release dust and dander on small particles that move about with eddy currents in the exhaust ducts when the cages are in the rack and elsewhere when the cages are out of the rack. Problems with this airborne vector can be partially dealt with by enclosing each of the cages by a cover that comprises a filter panel to block passage of dust and dander into or out of the cages, particularly when the cages are withdrawn from the rack system. However the cages must be opened to the air for service.
Removing the cages from the rack exposes the orifices to the air supply and exhaust openings to the air. Dust and dander can become entrained in the air moving about in the ducts in a manner similar to the way in which water borne diseases may move about in a circulating water system. Moreover, in a circulating water system one cannot simply disengage a tank from the system because the water otherwise supplied to the removed tank would be discharged onto the rack, floor or other tanks.
Leakage and inadvertent water discharge can be a problem in water tank housing. Apart from spillage, temperature and humidity constraints can make the air around a tank system uncomfortable for humans. Different types of fish require water at different temperatures. For zebrafish, the water should be maintained at about 85.degree. F. for optimum health and breeding conditions (specifically 25 to 31.degree. C. or 77 to 87.8.degree. F.). This is higher than room temperature, leading to high humidity levels, condensation of water on relatively cooler surfaces, and dripping water that may damage components of the housing, spread disease and create unpleasant working conditions for the humans that are involved.
There is a need for a housing system for fish that solves the foregoing problems and optimizes conditions of comfort and safety for aquatic animals and for people. Additionally the system should be convenient and inexpensive. Optimally, such housing is characterized by high animal density, that is, both housing a large number of fish or other aquatic animals in a relatively small volume of well serviced water, and also supporting the tanks or similar enclosures that hold the water in a very compact and space saving arrangement.